Revit is building information modeling (BIM) software that is used by architects, engineers, contractors and designers to design and document building projects. One key aspect of using Revit effectively is setting your project’s units properly. Units define the scale and precision of the model’s dimensions, as well as formats for annotations like text.
Being able to switch measurement units in Revit is important for collaboration, meeting local requirements, and converting legacy documentation. In this guide, we’ll cover everything you need to know about managing units in your Revit projects and models.
Overview of Units in Revit
Before diving into unit changes, let’s look at some basics of how Revit handles units:
- Revit allows you to define units for length, area, volume, angle, and other measurements independently.
- These units are project-wide settings that apply to all views and families in that file.
- Options include decimal units like meters/feet or fractional inches/feet.
- Unit formats like decimal places and display of units in text can be customized.
- Units are set on a per-project basis – there are no global application units.
- Changing units does not scale or modify geometry, just changes the reporting.
- Any annotations must be checked for position/sizing when switching units.
Understanding these principles will make managing units easier as we discuss changes below.
Why Change Units in Revit?
Some common reasons you may need to modify units in an existing Revit model or project include:
- Collaborating with international teams – Switching units to match collaborators using metric or imperial systems.
- Meeting local requirements – Adopting localized unit standards for a particular country or region.
- Client specifications – Delivering documentation in specific units required by the client.
- Coordinating with other software – Matching units to import/export properly to programs like AutoCAD.
- Updating office standards – Transitioning all models to new office unit guidelines.
- Converting legacy files – Importing old projects in different units and needing to modify them.
- Fixing incorrect settings – Correcting units that were defined incorrectly when starting the model.
In most non-trivial projects, you’ll likely need to change units at some point for a smoother workflow and improved coordination.
Accessing Unit Settings in Revit
All unit settings are managed through Revit’s Project Units dialog box. To access this:
- On the Manage tab, select Project Units from the Settings panel.
- This will open the Project Units dialog with all measurement options.
You can also access it through the Units button at the bottom of most Properties palettes if already working on an element. Managing units for your models starts here.
How to Change Units for Length in Revit
Length is the most common unit you’ll need to switch in Revit. This includes measurements for model geometry, annotations, detail dimensions, text, spacing, etc. Follow these steps:
- In the Project Units dialog, go to the Length section.
- Select your desired Length Type – Decimal, Fractional, or Feet & Inches.
- Choose your new Length unit from the dropdown – Meters, Centimeters, Feet, Inches, etc.
- Pick your Format – how many Decimal Places or Fractions to display.
- Check the box to Include Units in Length-based Text Fields if needed.
- Click Apply or OK to save the changes. Revit will now use the new length units.
Take extra care if your new units vary significantly from existing ones – model elements can resize and text spacing will shift. Check annotations after switching.
Changing Revit Area Units
To change the units for areas in Revit:
- In Project Units, go to the Area section.
- Pick your Area Type – Square Meters, Square Feet, Square Centimeters, etc.
- Set the number of Decimal Places to display for calculated areas.
- Enable the Include Units in Area Text Fields option if desired.
- Click OK to apply the new area units across your model views.
As with length, watcher for annotations and element sizing until you adjust. Room tags may need repositioning if area units change drastically.
Modifying Volume Units in Revit
Follow similar steps to modify the cubic volume units used in Revit projects:
- Go to Volume in the Project Units dialog.
- Select your Volume Type – Cubic Meters, Cubic Feet, Cubic Centimeters, etc.
- Set Decimal Places for calculated volumes.
- Turn on Include Units in Volume Text Fields to add units to tags.
- Save changes and test volume labels to confirm desired display.
Volume units are used less often than length/area but are still important for schedules, legends, tags, and some room calculations in Revit.
Changing Revit’s Angle Units
Angles in Revit, including slope and rotation, use degrees as the default unit in most cases. To modify:
- Go to Angle in Project Units.
- Pick your Angle Type – Decimal Degrees, Degrees/Minutes/Seconds, or Grads/Radians for specialized use.
- Set Decimal Places as needed for precision if using Decimal Degrees.
- Enable Include Units in Angle Text Fields to add degree symbols and formats.
- Alternately choose the Radians default unit for angular measurement instead of degrees.
Just take note that switching Angle units can affect angular dimension formatting. You may need to re-annotate any affected dimensions.
Other Revit Unit Types to Modify
In addition to core length/area/volume/angular units, Revit offers a few other unit categories you can modify:
- Currency – Units and formats for cost values and schedules.
- Slope – Rise and run units for representing slopes.
- Unit Scale – Scales content rather than changing displayed units.
- Duct/Pipe – Specialized units for MEP components.
Most projects won’t need to change these, but they provide advanced formatting options for broader applications of Revit like construction cost estimation.
Setting Project Units During Revit Setup
When starting a new Revit model, you have the opportunity to define units right at the beginning:
- On first opening a template, access Project Units as described above.
- Before placing any content, set all units as needed for your project.
- Check Include Units in Text Fields as desired.
- Click OK and build your model using these defined units.
Setting units upfront prevents any slowdowns later from converting content already created using incorrect units. Just be sure your template units match your intended project units.
Converting Existing Content to New Units
If you need to change units in an existing Revit model with lots of content already built, Revit will attempt to convert and rescale everything automatically when you modify the units:
- Length-based elements – Measurements for walls, floors, dimensions, spacings, etc will be converted to your new length units.
- Area and volume elements – Calculated areas/volumes will display using the new units.
- Text annotations – Text will resize and reformat based on the new units and settings.
- Model geometry – Physical elements will remain unchanged. Only the reporting units convert.
Not everything will rescale perfectly though, so expect to have to manually tweak some items, recreate text callouts, resize spaces, etc afterwards. Allow time for adjustments. Saving backups before converting units is recommended.
Best Practices for Changing Units in Revit
Follow these best practices whenever you need to modify units in a Revit project for the smoothest transition:
- Set units early for new models before adding content.
- Use whole number units like Feet or Meters to avoid decimal rounding issues.
- Use fractional Inches for drawing/detailing if needed rather than decimal feet.
- Delete and recreate text annotations after converting units rather than resizing.
- Adjust dimension text positioning manually after unit changes.
- Recheck room sizes and spaces that may rescale imperfectly to units.
- Save backups before altering existing models with lots of content.
- Triple check schedules and sheet sets for any hidden unit formatting issues.
- Adjust family unit settings to match project units before inserting into models.
- Ensure units match for linked models before importing into a project.
While Revit does a decent job converting units automatically, taking some extra care will prevent major formatting issues down the road.
Revit Units for Architecture vs MEP vs Structural
The optimal units to use in your Revit model can vary slightly depending on your discipline and application:
- Architecture – Decimal feet or inches for core model. Metric OK for large sites. fractional Feet & Inches for details.
- MEP/HVAC – Inches for ductwork. Feet ok elsewhere. Avoid decimal feet for fabrication.
- Structural – Decimal feet for core model. Inches on details. Meters sometimes used for large spans.
- Construction – Decimal feet or meters for core model. Inches for prefabrication.
- Civil – Survey/site data may use decimal feet. Meters can work for infrastructure.
Discuss with collaborators and partners to pick the right base units for your purposes. Just try to be consistent across disciplines on shared projects when possible.
Changing Units in Imported Revit Files
When importing Revit files into a project using Project Open or linking models, you may encounter unit mismatches with the current file. Here are some tips to resolve:
- Before importing, open the Revit file and change its units to match your main model.
- For minor unit differences, use Coordinates > Acquire Coordinates to align.
- If units vary greatly, import with Coordinates > Auto – Origin to Origin to try rescaling.
- Setting the host model to Unit Scale and scaling content can resolve unit mismatches.
- Worst case, delete and re-import the model after matching its units over to your main project file.
You want to avoid situations where two linked models have clashing units. The goal is making them consistent whenever possible for the full workflow.
Shared Coordinates and Units in Collaboration
For team collaboration across multiple Revit models, establishing shared coordinates and units from the start is recommended:
- Set consistent base point coordinates so models link up physically.
- Use matching units in all linked models and families. Avoid mixing.
- If units must vary, coordinate them section by section, floor by floor.
- Use shared project templates with pre-defined units. Never start from default.
- Have BIM managers review units before models get too far.
- Use shared coordinates at insertion point for families like doors/windows.
- Test coordinate data import/export between models to catch any unit errors.
Consistent units may not always be possible depending on consultant workflows. But minimizing unit conflicts will produce better merged Revit models and drawing sets.
Using Other CAD Software Units in Revit
Importing or linking data into Revit from other CAD programs also requires some unit awareness:
- When importing AutoCAD DWGs, ensure the drawing units match Revit before importing.
- For SketchUp, export using Revit’s preferred units like feet or meters.
- Revit and AutoCAD Architecture use the same units definitions, simplifying links.
- MicroStation units can be matched using master file setup on export and import.
- Rhino models may need unit rescaling before importing into Revit since units can vary.
So always keep track of underlying units in any CAD data used with Revit to avoid surprises. Match them whenever possible for seamless coordination.
Units for Revit Families
Shared Revit families also need proper units defined before placing into projects:
- Edit the family to use appropriate Length, Area, and Volume units.
- For annotative elements, set text to match the preferred units like feet and inches.
- Use Automatic – Family for insertion units when placing into models.
- If hosted elements, ensure global parameters match project units.
- Set family units consistently with your office template files.
Checking for unit consistency across both projects and families will minimize headaches in the long run!
Troubleshooting Problems with Revit Units
Here are some common unit issues in Revit along with troubleshooting tips:
Elements Displaying Wrong Size
- Check Project Units for conflicts with host model or linked files. Convert to match.
Text Not Scaling Properly
- Delete and recreate text rather than resizing after unit changes.
Incorrect Sheet Sizes
- Unit changes can resize sheets. Reset sheets to proper sizes after switching units.
Area Calculations Off
- Verify all connected elements are using consistent units, including linked models.
Imported Geometry Wrong Size
- Import with Auto – Origin or rescale geometry to match Revit model units on import.
MEP Spaces Don’t Fit
- A mismatch between decimal model units vs fractional MEP units can cause fit issues.
Model Links Shifting
- Reset both files to shared coordinates and consistent units before linking.
Following general best practices for units from the start and periodic checks for consistency can prevent many of these unit-related problems in Revit projects.
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Here are answers to some common questions that come up when working with units in Revit:
What are the main reasons to change units in an existing Revit model?
Typical reasons include matching office or client standards, coordinating with linked models, updating legacy files, converting units for fabrication, or fixing incorrect units defined initially for a project.
Is there a way to batch change units across multiple Revit files?
Unfortunately Revit does not have built-in batch tools for this. Units must be changed in each model file individually before combining via linking.
Do revit units affect the actual model geometry?
No, only the displayed values are affected when changing units in Revit. The physical model remains unchanged. Some annotations may need resizing afterwards.
Should separate consultants use the same Revit units on a project?
Ideally yes, for wall lengths, room sizes, and other core data to link up properly. But some firms use imperial vs metric units by profession, making it more complex.
What are the main unit options for lengths in Revit?
Common choices are decimal feet or meters, fractional inches or feet/inches, and metric units like centimeters for smaller elements. Format and precision can be customized.
What content has to be checked after switching Revit units?
Focus on text annotations, schedules, dimension sizes, sheet sizes, imported files, families, spaces between objects, and calculations based on the changed units.
Understanding how to modify units is an essential Revit skill for architects, engineers, and designers collaborating on complex building projects. While switching units can take some adjustments, mastering Revit’s unit settings gives you flexibility to meet requirements, convert legacy data, and enhance coordination.
Follow the steps provided to successfully change units for length, area, volumes, angles, and other values based on project and model needs. With the ability to fluidly adapt units, you can resolve tricky unit conflicts, match client deliverables, and optimize Revit workflows. Just remember to save backups before converting, and take time to check for annotation resizing.
Sticking to whole number units where possible, planning unit decisions upfront, and maintaining consistency across models and teams will lead to smooth unit coordination in Revit. Your building designs and documentation will be that much cleaner and efficient. Mastering units sets you up for Revit success.